Electric impulse transmitter pawl silencer



Se t. 12, 1950 w. T. WEIDENMAN I 2,522,004

ELECTRIC IMPULSE TRANSMITTER PAWL SILENCER Filed Dec. 24, 1947 INVENTOR. WILLIAM T. WEIDENMAN Z ms A zaeusxr.

Patented Sept. 12, 1950 UNITED STATES PATENT OFFICE ELEoTnro IMPULSE TRANSMITTER PAWL SILENCER William T. Weidenman, Spring Valley, N. Y., as-

signor to Telephonics Corporation, New York, N. Y., a corporation of New York Application December 24, 1947, Serial No. 793,668

operation is the familiar clicking noise caused by the dropping of the finger wheel pawl to the bottom of the teeth of the ratchet before the return spring rotates the ratchet wheel through the angle equal to the number of teeth corresponding to the digit dialed, causing the contacts to close an equal number of times to send that number f electrical impulses. Although this clicking is not loud, it is distracting and often disturbing, especially where the dial is in almost continual operation as by a telephone operator. Many expedients have been employed to eliminate or at least deaden the click, but they have either been inefiective or have impaired the efiiciency of operation of the dial in time.

In accordance with the present invention, a simple and inexpensive means is provided for virtually eliminating the clicking noise incident to the operation of the ratchet and pawl mechanism of a calling dial type of impulse sender,

without impairing the efliciency of the dial even after extended use, and without requiring attention or replacement of parts other than that normally required in any event.

The invention comprises an electric impulse transmitter having the usual: ratchet wheel and pivoted pawl, which i rotated by the finger wheel or dial in a, rearward direction until released so that the pawl engages a tooth to rotate the ratchet wheel, the ratchet wheel being grooved peripherally to at least the root circle of the teeth, and a resilient ring or disc is disposed in the groove for deformation by the pawl to deaden the impact thereof.

In the embodiment of the invention, the resilient ring or disc is thin axially so as to be defiected in one axial direction or the other by the pawl to intervene between the pawl and the bottom of the notch to thereby cushion the impact of the usual metal-to-metal contact between the pawl and the ratchet wheel, thus substantially eliminating the click of impact.

In a modification of the invention, the peripheral slot is substantially wider axially than the resilient ring or disc, so that upon impact of the pawl, the former is squeezed and spread laterally into the slot without deflection, so as to cushion 2 the impact of the pawl against the bottom of the notch to thereby substantially eliminate the click of impact.

It will be seen that the invention provides a very simple and inexpensive means for correcting the principal objection to impulse transmitters of the calllng' dial type, and that the invention may be applied to existing designs of dials 'withoutimpairing their efficiency or introducing an element of future difilculty.

For a more complete understanding of the invention, reference may be had to the accompanying drawings, in which:

Figure 1 illustrates a front view of a telephone type calling dial embodying the invention, a portion of certain of the parts being cut away in the interest of clarity;

Fig. 2 is an enlarged rear view of the ratchet and pawl mechanism of the calling dial illustrated in Fig. 1;

Fig. 3 is an enlarged transverse section through the pawl and ratchet mechanism, as seen along the line 3--3 of Fig. 2; and,

Figs. 4 and 5 are similar transverse sections of modifications.

Referring to Fig. 1, numeral 5 designates the finger wheel dial arranged with its finger holes above the number plate 6, and having a central opening keyed to a raised hub portion 8 of the plate '9 and'tc which it is held by means of a .screw threaded in the hole in the center of hub 8. & Hence, clockwise manual rotation of the finger wheel 5 results in the movement of plate '9 up tothe point where the finger engages stop" 7, whereupon the wheel 5 is released and is rotated counter-clockwise by a tension spring attached to shaft l5 at a speed controlled by the usual governor, not shown. This return movement of .dial 5 andv plate 9 is limited by the engagement of a projection on'plate 9 with the stop I3.

" Pawl I0 is pivoted at ll tothe plate 9 and is normally urged against and between the teeth ll of ratchet Wheel M by the coiled tension spring 12. As the finger wheel 5 is rotated inthe clockwise direction, carrying the plate 9 and pawl It with it, the ratchet wheel M remains stationary and the pawl Ill snaps over the ends and between the ratchet wheel teeth I'l. Upon the return movement of the finger wheel 5 the paw1 engages one of the teeth I1, thereby carrying the ratchet wheel !4 along with it and also rotating the gear l6 formed integrally with the ratchet wheel and adapted to operate the impulsing mechanism, not shown. The mechanism just described is conventional and well-known.

Ordinarily, as the pawl II] drops down into the notches between the teeth I1 on the ratchet I4, the familiar clicking noise ensues, owing to the metal-to-metal contact. In order to deaden and thus substantially eliminate this clicking noise, the ratchet I4 is provided with a peripheral groove l8, preferably extending slightly below the root circle of the teeth I1 as shown in Fig. 3, and in this slot I8 is inserted a soft rubber disc or ring I 9, which fits relatively closely within the slot It. The rubber ring or disc I9 is preferably made of a synthetic rubber of the type which is immune to deterioration by oil. The disc or ring I9 is thin, being on the order of .015 inch thick, the drawing being greatly exaggerated in the interest of clarity, both as to the width of the slot I8 and the rubber disc I9. It will be seen that being larger in outside diameter than the root circle of the teeth H, the rubber disc or ring I9 overlaps the radial surfaces of the teeth I! at opposite sides of the slot I8 and also bridges the notches between the teeth H, as is best shown in Fig. 2.

Instead of cutting the groove I8 through the ratchet teeth I! as shown in Fig. 3, the ratchet wheel I4 may be made of two parts riveted together by rivets 2| over a thin shim having a thickness equal to the width desired for the slot I8", as is shown in Fig. 5. The rubber ring or disc I9" is then inserted in the slot provided by the spacing afforded by shim 20 of the two halves of the ratchet wheel I4, and the ring I9 overlaps the ratchet teeth I! at opposite sides of the slot I8".

In operation of the form of the invention illustrated by Figs. 3 and 5, the pawl I0, in snapping over the teeth I1 into the notches between them, engages the free edge of the thin rubber ring or disc 19 and bends it over as shown at the bottom of Fig. 3, so that part of the rubber disc or rin I8 intervenes between the lower edge of the tooth or pawl II] and the bottom of the metal notch in ratchet I4. In this way, the rubber ring or disc I9 effectively cushions the impact of the pawl ID in the notches of the ratchet wheel I4 and thus eliminates the clickin noise during operation of the dial.

In a modified form of the invention illustrated in Fig, 4, the rubber ring or disc I9 is again made of resilient material, such as synthetic rubber but has a greater width than the ring shown in Fig. 3, as it is not required to be laterally flexible, but is required to be compressible. Thus, the width of rubber ring I9 in Fig. 4 is preferably .02 inch and the slot I8 is made wider, preferably 0.25 inch, for example. The slot I3 may be made as shown in Fig. 4, that is, .by cutting it through the teeth I! to a point slightly below the root circle thereof, as shown, or the slot 18' may be formed by a spacing shim 20, as indicated in Fig. 5, except that the shim 20 is made thicker so as to 4 afford a wider notch I8" than is shown in Fig, 5.

In operation of the modification shown in Fig. 4, the impact of the pawl II] on the rubber ring I9 causes it to be compressed and to spread or flow laterally to the full width of the slot I8, as shown at the bottom of Fig. 4, so that the rubber fills that part of the slot l8 which extends below the root circle of the teeth 'I'l. However, the cross-sectional area of the rubber ring I9 is somewhat greater than the cross-sectional area than that portion of the slot I8 which extends below the root circle of the tooth I! so that the rubber more than fills the said portion of the slot I8 and. extends slightly above it. Accordingly, the pawl I 0, in compressing the rubber I9, engages only the rubber and not the bottom of the notch between adjoining teeth IT in the ratchet I4 so that the clicking noise of the pawl impact is eliminated.

Although certain preferred embodiments of the invention have been illustrated and described herein, it is to be understood that the invention is not limited thereby but is susceptible of changes in form and detail within the scope of the appended claim.

I claim:

In an electrical impulse transmitter, the combination of a ratchet wheel having teeth around its periphery, a pivoted pawl adapted to engage the toothed periphery of said ratchet wheel, means for rotatin said pawl rearwardly over said ratchet wheel teeth and then to engage a tooth thereof to move the ratchet wheel with the pawl, said ratchet wheel having a peripheral groove extending radially inwardly through the teeth thereof to at least the bottoms of the notches between said teeth, and a ring of resilient material inserted in said groove and having a uniform outside diameter greater than the diameter of the root circle of said teeth, and being'axially narrower than said groove, said ring material having a resiliency such that the rin material temporarily deforms laterally to the width of said groove at the point of impact of said pawl thereon to thereby deaden the impact sound.

WILLIAM T. WEIDENMAN.

REFERENCES CITED The following references are of record'ln the file of this patent:

UNITED STATES PATENTS Number Name Date 436,440 Robinson Sept. 16, 1890 1,219,698 Brackett Mar. 20, 1917 2,133,469 Obergfell Oct. 18; 1938 2,276,514 Puckette Mar. 17, 1942 FOREIGN PATENTS Number Country I Date 2,700 Great Britain July 13, 1877 

